Fracture behaviour of cast in-situ TiAl matrix composite reinforced with carbide particles

Three-point bending tests, Charpy impact tests and numerical simulations were carried out to study fracture behaviour of in-situ TiAl matrix composite reinforced with Ti2AlC particles prepared by centrifugal casting of Ti-44.5Al-8Nb-0.8Mo-0.1B-5.2C (at%) alloy. The brittle fracture behaviour of the in-situ composite includes crack deviation, microcrack formation, carbide fragmentation, delamination on the matrix-carbide interfaces and pull-out of the carbide particles from the TiAl matrix. The crack initiation and propagation is related to applied load, deflection and acoustic emission events measured during three-point bending tests. A critical stress leading to a crack initiation in the notch region is numerically calculated for quasi-static loading conditions using finite element analysis (FEA). The measured fracture toughness values are comparable to those of some in-situ TiAl matrix composites prepared by casting and reactive processing.